Coral Reef Ecosystem Microbiology

Diel dynamics of dissolved organic matter production and remineralization as a driver of coral reef nutrient recycling (National Science Foundation, 2020-2023)

Collaborators: Linda Wegley Kelly @ SDSU

Summary: Coral reefs exhibit some of the highest rates of primary production and decomposition of any ecosystem type yet persist in some of the most oligotrophic waters on the planet, implying tight recycling of macronutrients through organic matter. Roughly one third of gross benthic production in reefs is released as dissolved organic matter (DOM), yet reefs exhibit depleted DOM relative to the surrounding ocean, suggesting that rapid microbial consumption and remineralization processes of DOM play a significant role in nutrient recycling. Our recent documentation of significant diel shifts in both microbial communities and nutrients in reefs suggest that dynamics of microbial-DOM interactions on short daily timescales may be a fundamental feature of reefs that play a key role in nutrient recycling and retention. This project will define in situ diel dynamics of microbial communities and dissolved organic and inorganic nutrients in a coral reef system and then further resolve specific microbial-DOM genomic- metabolomic interaction mechanisms that drive the transformation and remineralization of metabolites involved in nutrient recycling in reefs. Key products of this work will be to develop a core understanding of diel microbial ecology and biogeochemistry in reef ecosystems and to use this understanding to illuminate key microbial and molecular players in the nutrient decomposition and remineralization processes long hypothesized to be central to maintaining healthy reefs.

Developing untargeted molecular networking as a tool to characterize widespread transformations of marine dissolved organic matter

Collaborators: Linda Wegley Kelly @ SDSU, Lihini Aluwihare @ SIO, Pieter Dorrestein @ UCSD, Andi Haas @ NIOZ

Publications: Petras et al. 2017

Summary: Carbon cycling in the ocean is centered on the reactivity of complex pools of marine organic matter (hundreds of thousands of different molecules) processed through the microbial food web. The overarching objective of this project is to develop novel approaches to define widespread transformations of marine DOM, associate these molecular transitions with distinct molecular families, and link these transformations to fates of recently produced DOM and distributions of semi-labile DOM in natural ecosystems. Such a goal requires bridging organic chemistry and microbiology methodologies to link microbial activity to molecular transitions through the DOM pool. By integrating laboratory and field experiments and oceanographic surveys paired with the development of analytical tools for untargeted metabolomics and metatranscriptomics we propose to characterize the fate of reactive DOM. A key product of this research is a refined mechanistic understanding of DOM-microbe interactions through the quantification of major microbially-mediated chemical transformations and metabolic pathways that influence the post-production processing of DOM.

NOAA Pacific Reef Assessment and Monitoring Program

We participate in this program to survey all US coral reefs in the Pacific once every three years, providing characterizations of microbial communities and organic biogeochemistry.

https://origin-apps-pifsc.fisheries.noaa.gov/cred/pacific_ramp.php

Moorea Coral Reef Long Term Ecological Research Program

Nelson is an Associate Investigator on this large, multi-investigator project contributing to understanding of the microbiology and organic geochemistry of this complex ecosystem

http://mcr.lternet.edu/